DocID031629 Rev 1

13/27

PM8804

Applications information

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On the contrary using the internal HV regulator without the auxiliary winding increases the

internal power dissipation, and in case of high ambient temperature and high power

MOSFETs to drive, this may lead the device into thermal shutdown.

5.2

Oscillator and FSW pin

The internal oscillator frequency can be programmed by connecting an external resistor

RFSW between the FSW and AGND pins.

The relationship between the oscillator frequency FSW and the RFSW resistor is:

Equation 1

The PWM switching frequency is equal to the programmed oscillator frequency.

The useful range for switching frequency is from 100 kHz to 1 MHz. This can be obtained

using a resistor RFSW in the range from 20 k to 250 k.

Figure 4. Switching frequency vs. RFSW

FSW kHz



24000

3.5 RFSW k



+

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